Weathering the Storms: How PVF Film Technology Preserves and Elevates Building Exteriors

In an accelerated and real-time test, PVF film proves a multitude of aesthetic and structural benefits
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Sponsored by DuPont™ Tedlar®
By Erika Fredrickson
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Lab Testing and Resistance

PVF film has extremely high chemical resistance and compatibility with acids, bases, oxidizers, and a variety of solvents, including polar, non-polar, aromatic, aliphatic, hydrocarbon and chlorinated solvents, and other harsh chemicals. Even under extreme conditions with high concentrations, extended exposure times, and high temperatures, the PVC film retains all or most of its original properties and appearance. In a series of accelerated and long-term lab tests—some of which lasted hours; some months and years—PVF was immersed various times between 77 degrees Fahrenheit and boiling temperatures in acids, bases, solvents, and miscellaneous chemicals. The result was that there was no perceptible change in either appearance or mechanical properties to the film, except for a slight change from bleach after a month. The tests show both a resistance and compatibility with these chemicals. Though it was not an exhaustive list of all possible chemicals a film might encounter, it was an extensive one using a broad range of chemistries, simulating conditions that were well beyond any real exposure conditions that the film would endure in the real world, demonstrating its extreme robustness.

In other lab tests, PVF proved to be impermeable to greases and oils. This makes the films easy to clean because so many staining agents remain on the surface of the films rather than seeping into the material. They can be easily removed by cleaning without the cleaning process leaving behind shadow ghosting streaks.

When stain removal is necessary—and it is probably necessary in any industry—PVF film offers one solution to address staining so that materials do not need to be replaced. It has excellent resistance and is easily cleanable. In one test, a variety of potential staining agents were placed on the surface of PVF film and left for 24 hours prior to cleaning. The residue was then wiped first with a dry cloth, followed by a wet cloth, then mild detergent, moderate household solvents such as isopropyl alcohol, and finally as needed, stronger solvents such as acetone, toluene, or MEK. After the test was done, the PVF film had no changes in appearance or mechanics.

Stains come in all kinds of forms, including food and drink, household items, or even chemicals. Each stain removal may require a different cleaning agent, and each cleaning agent has a different chemical makeup. Since PVF films can be compatible with many aggressive solvents, an entire range of cleaning products can be used without worry of permanent material damage. This includes even the harshest cleaners found in industrial applications for tough stain and graffiti removal.

Cleaning removes dirt, debris, and other matter from the surface of the film, but it often does not kill bacteria, viruses, fungi, or other pathogens that can persist on the surface. In many public areas and especially health-care settings, proper disinfection after cleaning is vital to ensuring public safety and controlling the spread of disease. Disinfection is most often performed by exposing surfaces to chemical disinfectants, but sometimes it is also supplemented with exposure to UV light. When used on PVF film, chemical disinfectants should be employed as described on their labeling.

Resistance to mold, mildew, and fungus also was tested in labs using two standard tests. ASTM G21, the standard practice for determining resistance of synthetic polymeric materials to fungi, was conducted by placing samples onto the surface of nutrient agar and spraying it with a mix of spore suspension made up of five fungal strains: Aspergillus brasiliensis, Penicillium funiculosum, Chaetomium globosum, Trichodermavirens, and Aureobasidium pullulans. These samples were incubated for four weeks and observed at the end of each week. Agar has everything it needs in terms of trace nutritional elements to support fungal growth, but in order for it to work, it needs a primary carbon source. The PVC would need to provide that nutrient source for any microorganism to grow. However, even after the four-week test, the PVF film only showed trace growth—not enough to sustain substantial growth or fungus, mold, or mildew.

UL 2824, the standard method for measuring microbial resistance for various sources using static environmental chambers, is a part of the annual UL GreenGuard Certification Program that recognizes products exhibiting superior performance for indoor air quality. In this test, the PVF was placed in a sterile petri dish and inoculated with a known concentration of Penicillium brevi-compactu. The dish was placed in an environmental chamber at 95 percent humidity and 77 degrees Fahrenheit for three weeks. At the same time, a positive control sample susceptible to fungal growth was run as a test to verify microbial activity. Colony-forming units (CFUs) are counted at the beginning and end of the test, and a rating is provided. The PVF achieved the highest rating, showing its high resistance to mold growth.

PVF films are created without plasticizers, processing aids, or other additives that can be a nutrient source for microbes. They also do not appear to support bacterial growth, even in tests where they are placed in agar inoculated with Pseudomonas aeruginosa. In this test, the samples and negative control samples were incubated for 28 days at 82–86 degrees Fahrenheit and evaluated for visible evidence of growth. The results showed there was no growth on or around all five replicate samples, showing the specimens do not contain nutritive components for this bacterium.

While PVF films do not contain nutritive components that support the growth of mold, mildew, fungus, and bacteria, microbes still can find their way to the surface of the material from the environment. To eliminate these microorganisms from the surface, the surface must be cleaned and disinfected. PVF films have outstanding chemical resistance and durability to withstand repeated cleanings with even the harshest chemicals and disinfectants. The resistance of PVF films to several common disinfectants used in a health-care setting was proven. The surface exhibited no cracking, delamination, or changes in either color or gloss after five days of continuous contact. The resistance to growth of mold, mildew, fungus, and bacteria is complemented by the outstanding chemical resistance and ease of cleaning and disinfecting. This combines with the durability, versatility, and timeless aesthetics to provide unique surface protection with unparalleled performance, both indoors and out.

Finally, it was important to test how much water might have a chemical breakdown effect on PVF films over time, considering rain and snow conditions and especially places with extreme precipitation. In one hydrolysis resistance test, the PVF was run through an accelerated stress test at 250 degrees Fahrenheit and 100 percent relative humidity. Even after 100 hours of this harsh environment, the films showed no change in mechanical properties or color. In another longer-term test, the PVF was exposed to 185 degrees Fahrenheit and 100 percent relative humidity for 4,000 hours. Afterward, the films showed very little change in mechanical or color stability. The tests showed PVF films do not readily absorb water and are highly resistant to degradation by way of hydrolysis, even under extreme and unlikely weather.

A True Test of Time Case Study: Pullman Hotel, Paris

This skyscraper hotel located in central Paris—designed by Pierre Dufau et Associés and built in 1974—has had several different owners, from the Sheraton to the Méridien, before finally becoming the Pullman Hotel Montparnasse in 2011. The hotel’s interior has gone through some major changes to refurbish it and keep it from falling into disrepair. In 2020, it went through a 24-month renovation that modernized the hotel’s 953 rooms as well as its meeting center and common areas, bringing it back to life and updating its overall look.

But the exterior of the 31-story hotel has remained the same since it was built. Its 18,000-square-meter facade features steel cladding laminated with PVF film. It is shaped into vertical, angular lines that seem to reach toward the sky and gleam in elegant silver. The PVF application of galvanized sheet steel laminated with white film installed when the hotel was built remains untouched—no sign of the yellowing, chalking, or corrosion seen on metal without PVF. This has allowed the hotel to maintain its original style and beauty for generations as a recognizable Parisian landmark—with no substantial cost to the hotel’s many owners.

PVF film resists chemicals, abrasions, mold and mildew growth, and can be cleaned by disinfectants without showing signs of harm—and in terms of exteriors, it provides the kind of durability that a building needs to operate in a cost-effective manner.


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Originally published in Architectural Record
Originally published in July 2021